Crazy temperature gauge

[Rikk]

Hi..I’m Rick and I joined to maybe get some advice about my Hymer 544 on a ducato base ( 2002 2.8 diesel )for a while the temp gauge has played up going to hot (straight up) then returning when it felt like it. The other day when the motor was not hot it went crazy buzzing round all over the place then stopped actually facing the speedo! So now it doesn’t work at all and I wonder if anyone has any advice for me. TIA. Rick